Possible Explanations for the Observed Rise in the Incidence of Lung Adenocarcinoma relative to that of Lung Squamous Cell Carcinoma

The observed rise in the incidence of lung adenocarcinoma relative to lung squamous cell carcinoma has been claimed to result from changes in cigarette design associated with the shift to lower tar filter cigarettes. We present evidence that tends to undermine this claim. In particular, a recently published review based on extensive data has shown that there has been a substantial rise in the relative frequency of adenocarcinoma compared to squamous cell carcinoma in those who have never smoked.